Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals.

The correlation between local mechanical (elasto-plastic) and structural (composition) properties of coal presents significant fundamental and practical interest for coal processing and for the development of rheological models of coal to coke transformations. Here, we explore the relationship between the local structural, chemical composition, and mechanical properties of coal using a combination of confocal micro-Raman imaging and band excitation atomic force acoustic microscopy for a bituminous coal. This allows high resolution imaging (10s of nm) of mechanical properties of the heterogeneous (banded) architecture of coal and correlating them to the optical gap, average crystallite size, the bond-bending disorder of sp(2) aromatic double bonds, and the defect density. This methodology allows the structural and mechanical properties of coal components (lithotypes, microlithotypes, and macerals) to be understood, and related to local chemical structure, potentially allowing for knowledge-based modeling and optimization of coal utilization processes.

Accurate and Precise Coulometric Determination of Sulfur Dioxide in Compressed Gas Mixtures.

Coulometry has been established as an important and reliable method for the determination of acidic compounds. The analytical method and simple apparatus described here arc applied to the precise and accurate determination of sulfur dioxide in nitrogen, specifically in compressed gas cylinders at nominal concentrations of 50 and 100 µmol/mol (ppm). This method is constant current coulometry where the magnitude of the current is set by the balance between the electrochemical generation of OH-, the flow of SO2, and the chemical reaction of the solution. The method is direct, rapid, and can be refined further to provide analysis at the nanomol/mol level.

Development of a Coulometric Method for Assessing the Concentration of Ambient Levels of CO2/Air in Compressed Gas Mixtures.

The coulometric method presented here is a reliable method for the direct analysis of CO2/air cylinder gas mixtures. It is based on Faraday's laws of electrolysis and therefore no external standardization is required. A series of CO2/air cylinder gas mixtures ranging in concentration from 300 to 375 µmol/mol (ppm) were analyzed and the results compared to those results obtained by non-dispersive infrared (NDIR) analysis with traceability to gravimetric standards. The coulometric method is rapid, sensitive, precise, and with the proper experimental controls, will yield accurate results.

Assessment of mitral flow velocity with exercise by an index of stress-induced left ventricular ischemia in coronary artery disease.

Exercise-induced myocardial ischemia results in both diastolic and systolic left ventricular (LV) dysfunction. To investigate the utility of Doppler assessment of LV diastolic function with exercise, 28 consecutive patients underwent digital stress echocardiography, including measurement of mitral flow velocity by pulsed-wave Doppler and simultaneous stress thallium imaging. The mean mitral flow velocity was measured as the integrated area under the LV diastolic inflow Doppler spectral display. The change in mean mitral flow velocity from baseline to immediate postexercise was compared among 3 patient groups: (1) patients with thallium redistribution or exercise-induced wall-motion abnormalities, or both, consistent with exercise-induced ischemia (n = 18), (2) patients with no evidence of stress-induced ischemia, with or without resting wall-motion abnormalities (n = 10), and (3) 10 control subjects of similar age with normal resting 12-lead electrocardiograms, normal resting and postexercise 2-dimensional echocardiograms and normal electrocardiographic treadmill stress testing. The percent increase in mean mitral flow velocity was 101% (+/- 59) for controls and 86% (+/- 53) for patients without stress-induced ischemia versus 33% (+/- 24) in patients with stress-induced ischemia (p less than 0.005). An increase in mean mitral flow velocity with exercise of greater than 50% correctly identified 9 of 10 nonischemic control patients. An increase in mean velocity of less than 50% predicted ischemia in 15 of 18 patients with evidence of stress-induced ischemia (p less than 0.005) Thus, Doppler assessment of LV diastolic function with exercise expressed as a change in the mean velocity of mitral flow is a useful indicator of stress-induced ischemia.

In vitro fertilisation: the major issues--a comment.

KIE: Mitchell, a sociologist, comments on a companion paper on in vitro fertilization by Peter Singer and Deane Wells. He criticizes the failure of Singer and Wells to consider the deleterious effects on society and on the children of artificial reproduction involving donated sperm or ova and accuses them of placing the desire of the individual to have a child above the good of society and of future generations. Singer, in a brief response, defends his utilitarian argument that reproductive technologies should be available to all. He does not consider knowledge of one's genetic identity to be a crucial issue, pointing out that the child's alternative is no existence at all.^ieng

Letter: Kilopascals. Control of oral contraceptive clinical trails.

PIP: To deal with the confusion surrounding clinical acceptability of specific oral contraceptive preparations, a single set of forms for use in clinical research, together with a set of definitions, was recommended. Senior representatives of major pharmaceutical companies engaging in clinical trials in the United Kingdom were invited to cooperate. The Family Planning Research Unit of the University of Exeter was requested to provide facilities for meetings which began in 1972. An agreed set of forms has been designed and set of definitions has been developed to make the collection and interpretation of data more efficient. Organizations carrying out oral contraceptive clinical trials are invited to contact this unit. Forms, definitions, and further information will be provided on request.^ieng